The present invention relates to flow meters and in particular flow meters which can be utilized to determine if the liquid flowing through a piping system associated therewith is flowing under turbulent or laminar flow conditions.
Water flowing turbulently is much more efficient at removing heat in a cooling system than water flowing under laminar flow conditions. However, once turbulent flow is obtained increasing the flow rate further does not appreciably improve the cooling rate of the system. In molding applications, many mold operators unnecessarily try to maximize the flow of water through their cooling systems to ensure turbulent flow. Doing so simply increases the energy costs for pumping more water than necessary through the system and possibly limiting the amount of cooling water available for cooling additional molds on the same cooling system circuit.
Whether the flow of water through a pipe or channel is turbulent depends on the diameter of the pipe, the flow rate of the water through the pipe and the temperature of the water. For a pipe or cooling channel of known diameter, if the temperature of the water is known, one can determine what flow rate would be required to obtain turbulent flow. More specifically, the volumetric flow rate times the pipe diameter divided by the kinematic viscosity (which is temperature dependent) produces what is referred to as the Reynolds number. A Reynolds number of approximately 3500 or more is understood to be indicative of turbulent flow.
Injection molds generally have cooling water channels of a fixed diameter. The diameters for different molds vary but standard diameters are ¼, ⅜ or ½ inch. A preferred type of flow meter currently in use is a variable area flow meter having a float, piston or other movable flow indicator, slidably mounted on a conical post within a clear cylindrical tube. The piston is restrained from flowing out the distal end of the cylindrical tube by a spring. Water flowing through the chamber pushes the piston toward the distal end of the chamber against the force of the spring. The greater the flow rate, the more the piston compresses the spring and moves toward the distal end. A brightly colored band or indicator band extending around the piston is visible through the clear cylindrical tube and through a window or sight formed in the flow meter body. A scale printed along the side of the sight, indicates the flow rate therethrough such as in gallons per minute. See generally U.S. Pat. No. 4,619,139.
Utilizing existing flow meters, the current practice for determining whether the flow through the associated piping system is turbulent involves first determining the flow rate of the fluid therethrough using the flow meter. The flow rate measurement is used with the temperature of the fluid flowing therethrough and the size of the conduit to determine a Reynolds number for the fluid flowing therethrough. The Reynolds number is typically obtained from a standard chart or the like. However, such a system is somewhat time consuming and is not conducive to allowing a quick determination of whether the flow rate selected will result in turbulent flow through the system. There remains a need for a flow meter which can be used by a user to more readily determine whether the fluid flowing through a piping system associated therewith is flowing under turbulent flow conditions and to set the flow rate accordingly. It is also foreseen that there are likely to be applications for such a device which can be used by a user to determine whether the fluid flowing through a piping system is flowing under laminar flow conditions.